Flotation machines are commonly employed to separate solid material from a slurry typically composed of liquids and solids in varying proportions. An impeller located in the flotation machine agitates the slurry dispersing entrapped gas, thereby causing the formation of gas bubbles. Particulate solid material adheres to the surface of the gas bubbles and rises therewith to the slurry surface forming a froth that has a higher concentration of adhered solid material, than does the slurry.
The froth, which is a combination of liquid, solid particles, and gas is removed from the flotation machine for further processing. The gas bubble/particle interaction is important to the flotation process as, without it, there can be no separation via the above-described method. To generate sufficient gas bubbles and thereby froth, gas is usually introduced through an opening in the impeller or rotor of the flotation machine. A prior art method of introducing the gas is shown in FIGS. 1, 2, and 3. Gas is introduced through apertures 12 in the rotor. These apertures tend to be large and located between successive pairs of rotor blades 14. The apertures 12 extend, in part through an upper surface 16 of the rotor 10, with the remainder of each aperture extending into a body portion 18 of the rotor.
During operation, particles tend to travel up the rotor body portion 18 following the contours thereof. The contours are generally smooth with no discontinuities or protuberances between successive rotor blades 14. As such, the peripheral edges of each aperture 12 follows the smooth contours of the rotor body portion 18.
A problem associated with rotors configured in the above-described manner is that there is a tendency for solid particles, to enter the rotor body portion 18, through the apertures 12. Another problem attributed to these prior art rotors is that the distribution of gas bubbles attributable to the air entering through an aperture is not optimal due to the apertures configuration. This in turn minimizes the gas bubble/particle interaction and thereby the solid/liquid separation.
Based on the foregoing it is the general object of the present invention to provide a flotation machine rotor that overcomes the problems and drawbacks of prior art rotors.
The present invention resides in one aspect to a flotation machine rotor that includes a body portion which defines an interior area and is adapted to communicate with a gas source. At least one rotor blade projects radially outwardly from the body portion with at least one aperture being defined by the body portion. The aperture is in gaseous communication with the interior area and is adjacent the at least one rotor blade. During operation, gas flowing from the gas source is expelled through the aperture causing bubbles to be generated in a liquid/solid slurry in which the flotation machine rotor is immersed. The aperture is defined at least in-part by a lower peripheral edge. At least one lip projects outwardly from the lower peripheral edge. As the rotor operates, solid particles forming part of the liquid solid slurry travel upwardly along the body portion and encounter the lip. The solid particles are then projected away from the body portion and into approximate alignment with the aperture. The gas bubbles generated by gas being expelled from the aperture entrain the solid particles thereby forming a froth of gas bubbles and entrapped particles on the slurry surface which is then skimmed off, clarifying the slurry.
Preferably, the aperture is in the form of a slot and extends in a longitudinal direction approximately perpendicular to a central axis defined by the rotor. In the preferred embodiment of the present invention there are a plurality of slots each having a lip projecting from a lower peripheral edge of each slot. In addition, the body portion can be contoured with a diameter defined thereby progressively increasing from a lower to an upper section of the body portion. The slots are positioned in the upper section of the body portion.
The present invention resides in another aspect in a method for operating a flotation machine rotor of the above-described type wherein a liquid/solid slurry is introduce into a flotation machine and the rotor is caused to spin about the central axis so that the solid partides forming part of the slurry move upwardly along the body portion and contact the lips associated with the apertures in the body portion. At least a portion of the solid particles are projected radially away from the rotor by the lip and become approximately aligned with the associated aperture. Gas from the gas source is caused to flow from the aperture thereby forming bubbles in the slurry that define a surface upon which a portion of the solid particles projected from the lip contact and are entrain thereon. These bubbles and entrained solids cause a froth to form on the surface of the liquid solid slurry which can then be removed from the flotation machine.
FIG. 1 is a perspective view of a prior art flotation machine rotor.
FIG. 2 is a partial, bottom view of the rotor of FIG. 1.
FIG. 3 is a partial, cross-sectional view of the rotor of FIG. 1.
FIG. 4 is a perspective view of a flotation machine rotor embodying the present invention.
FIG. 5 is a bottom plan view of the rotor of FIG. 4.
FIG. 6 is a partial, cross-sectional view of the rotor of FIG. 4.
FIG. 7 is an enlarged view of a portion of the rotor of FIG. 7.
FIG. 8 is a partial bottom plan view of an alternate embodiment of the present invention.
FIG. 9 is a perspective view of the embodiment of FIG. 8.